1. Field of the Invention
The present invention relates to a car air conditioner, and, particularly relates to a controller for use for the car air conditioner.
2. Description of Related Art
There have been various apparatuses used as a conventional backup apparatus at the time of occurrence of a failure in a controller of a car air conditioner one is an apparatus in which a control mode is selected correspondingly to the operating state of an engine as described in Japanese Patent Unexamined Publication No. Sho-57-147908; another is an apparatus in which a failure judging means is provided in a controller to make it possible to open a bypass valve upon occurrence of a failure as described in Japanese Utility Model Unexamined Publication No. Sho-59-136569; another is an apparatus in which an electromotive clutch is switched off upon the occurrence of high-speed rotation of the engine to stop a compressor or to operate the compressor with the capacity reduced or to limit the compressor to a small-capacity side as described in Japanese Patent Unexamined Publication No. Sho-59-205553; another is an apparatus in which the capacity of a compressor is reduced when the engine revolution speed is not more than a predetermined value as described in Japanese Patent Unexamined Publication No. Sho-57-175423; another is an apparatus in which the capacity of a compressor is controlled on the basis of two values of the air temperature just after the passage through an evaporator and the necessary blowout temperature as described in Japanese Patent Unexamined Publication No. Sho-62-94748; and so on.
There has been various conventional apparatuses for preventing the change of the temperature of air in a downstream side of an evaporator. One is an apparatus in which the operating mode of a compressor is switched to minimize the fuel cost in response to an engine revolution speed detection signal and an idle detection signal as signals indicating the state of the car as described in Japanese Patent Unexamined Publication No. Sho-60-82427; another is an apparatus in which the capacity of a compressor is changed by detecting the change of the condenser temperature as well as the change of the evaporator temperature as a state of the cooler cycle as described in Japanese Patent Unexamined Publication No. Sho-63-25456; another is an apparatus in which a capacity control constant is switched on the basis of information as to whether the evaporator downstream air temperature is in an allowable temperature range including its target value as described in Japanese Patent Unexamined Publication No. Sho-64-49852; another is an apparatus in which the capacity control rate is reduced in the case where hunting occurs in the capacity control rate of a compressor at the time of stabilizing the operating state as described in Japanese Patent Unexamined Publication No. Sho-63-285282.
The conventional technique as described in the Japanese Patent Unexamined Publication No. Sho-57-147908 and the Japanese Utility Model Unexamined Publication No. Sho-59-136569 does not consider minimizing the influence of a blowout air temperature and the like on persons riding in the car when the engine revolution speed signal or the air temperature signal just after the passage through the evaporator is stopped because of breaking of wires or the like or when the capacity of the compressor is fixed at its maximum because of a failure of the capacity controller. Accordingly, a problem arises in that the performance of the conventional apparatus using a fixed-capacity-type compressor is deteriorated upon occurrence of a failure.
In the conventional technique as described in the Japanese Patent Unexamined Publication No. Sho-57-147908, there is no consideration of sending signals to external devices to ask for assistance of the external devices. In the conventional technique as described in the Japanese Utility Model Unexamined Publication No. Sho-59-136569, there is no consideration of a backup upon a failure of the controller. Accordingly, is a problem in that the compressor with a large capacity is continuously operated upon occurrence of a failure of the controller so that the evaporator is frozen making ventilation impossible.
In the conventional technique as described in the Japanese Patent Unexamined Publication No. Sho-60-82427, the evaporator downstream air temperature is changed by the change of the state of the car. Accordingly, a problem arises in that an uncomfortable feeling results from the change of the air temperature. In the conventional technique as described in the Japanese Patent Unexamined Publication No. Sho-63-25456, the temperature is changed by the change of the state of the cooler cycle. Accordingly, a problem arises in that an uncomfortable feeling results from the change of the air temperature.
In the conventional technique as described in the Japanese Patent Unexamined Publication No. Sho-64-49852, the response time constant and the like of the cooler cycle is changed with the state of the cooler cycle such as the outside air temperature. Accordingly, the hunting of the evaporator downstream air temperature cannot be reduced sufficiently. Accordingly, a problem arises in that an uncomfortable feeling results from the change of the air temperature. Further, in the conventional technique as described in the Japanese Patent Unexamined Publication No. Sho-63-285286, the evaporator downstream air temperature is changed correspondingly to the hunting when the hunting occurs in the capacity control rate of the compressor. Accordingly, a problem arises in that an uncomfortable feeling results from the change of the air temperature.